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BLACK RUST ON GALVANISED STEEL

I am a b.tech student of Indian Institute of Technology Roorkee, India.I am interested to know why does black rust appear on galvanised steel when it is kept or transported for long time.the microstructure of the black spot shows no zinc layer on it.This patching leads to a lot of wastage of steel and hence a solution to this problem will be a help to everyone .

PRASHANT KUMAR Singh
student - Roorkee, Uttaranchal, India
2007

I think no one has the slightest idea as why these black spots occur on cold rolled galvanised steel coils so let me share what I could find within these days
1> chances of black spots being Fe3O4 is still high.
2> pickling may be one of the reasons because of which Zn is unable to adhere properly to the surface.
however I still do not know the actual reason please help me

PRASHANT KUMAR Singh
- Roorkee, Uttaranchal, India
2007

adv.
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